1. Field of the Invention
The present invention relates to rodenticides and more particularly to the use of compositions containing certain pyridyl phenyl carbamates or their acid salts or metal salt complexes for the control and extermination of pest rodents.
2. Description of the Prior Art
The common rat, Rattus norvegicus, is vicious and constantly poses a serious threat to the health and well being of man. Rats and mice are destructive animals and a serious nuisance, causing millions of dollars damage annually to farms, agronomic crops, homes, food processing plants and many other businesses. Rats bite at least 14,000 (possibly up to 60,000) people every year in the U.S.A., according to the U.S. Public Health Service, and are known carriers of over 35 contagious diseases including bubonic plague, trichinosis, typhus, rat bite fever, amoebic dysentery, tuberculosis, infectious jaundice and rabies. During the years from 1898 to 1923, almost 11 million deaths were caused by rat-borne plagues.
Use of rodenticides, fumigants, sprays and traps are the primary methods employed for the control of pest rodents. By "pest rodents" we refer not only to members of the order Rodentia but also to those of Lagomorpha, which cause health hazards or economic loss unless kept in check. Rodenticides may be used in the form of a tracking powder or a bait or may be applied as a spray on the rodent's natural foodstuffs. The rodenticides used as a bait are of two classes: single-dose and multi-dose. Multi-dose rodenticides are usually selected over single-dose rodenticides, as they have been safer in the past than the available single-dose rodenticides. The multi-dose rodenticides are anti-coagulants, including a number of different 4-hydroxy coumarin and 1,3-indandione compounds. These multi-dose rodenticides consumed in small daily amounts have a lethal effect on rats and mice after liver stores of viatmin K have been depleted. Anti-coagulants are less effective on mice than rats, as mice are considered to be nibblers and may not consume an adequate amount of treated bait to have a lethal effect. A single-dose rodenticide which would be relatively safe to the person handling the material and to non-target species of animals and yet effective on a variety of pest rodents is highly desirable.